1. Field of the Invention
This invention relates to an apparatus and method for unloading from cargo holds or hoppers, cargoes of solid particulate material, especially those referred to in the trade as "sticky".
Particulate material has characteristics which make it difficult to unload from hoppers because of the arching or bridging phenomenon.
2. Description of the Prior Art
The arching or bridging phenomenon is discussed in some detail in U.S. Pat. No. 3,797,707, Jenike and Johanson (1974). The problem of unloading particulate material from hoppers and means of overcoming it is also discussed in "Bulk Solids Handling (The International Journal of Storing and Handling Bulk Material)", Vol. 5, No. 3, June 1985, published in English by Trans Tech Publications, D-3392 Clausthal-Zellerfeld, Federal Republic of Germany. See specially pages 623, 627, 629 and 633 to 640. See also the chapter "Self-Unloading Vessels" by Walker at pages 565 to 569. The literature referred to is hereby incorporated by reference.
Self-unloading seagoing and lakegoing vessels which carry particulate materials in bulk are equipped with large elongated hoppers having inwardly and downwardly sloping sides leading to an outlet overlying a conveyor. A simplified view of a self-unloading vessel is contained in U.S. Pat. No. 2,815,134, Borrowdale (1957). The vessel illustrated is, of course, much smaller than the typical vessels the applicant is talking about and only two side-by-side hopper outlets are shown, but the patent does serve to give a general idea of the type of vessel to which the invention applies and of the unloading problem.